This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. AIDS-related Kaposi's sarcoma (KS) is the major AIDS-related malignancy. It is believed that an interaction between the retrovirus, HIV, and the herpesvirus, Kaposi's sarcoma-associated herpesvirus (KSHV), results in disease pathogenesis. KSHV-infection and KSHV-related malignancies are newly emerging diseases which are prevalent in the Mediterranean and Sub-Saharan Africa but are spreading into the U.S. and Europe. It is believed that SRV-2 related retroperitoneal fibromatosis (RF) which is associated with the KSHV-like herpesvirus, RV1 rhadinovirus, RFHVMn, is a unique animal model for understanding the interactions of retroviruses and herpesviruses in the induction of tumorigenesis. Understanding virus transmission and tumor initiation in this animal model would provide unique information concerning both the human and macaque diseases which is an essential prerequisite to developing treatments for KS. In this project, we propose to establish the baseline parameters of the infectious cycle of the macaque RFHV and the closely related macaque RV2 rhadinoviruses. To determine if these viruses play a role in the development of retroperitoneal fibromatosis (RF) we will characterize their infectious cycles and the perturbation of these cycles by SRV-2 and other immunosuppressive agents. We will study virus transmission and the host response to infection. Study populations will include macaques with either active, latent or experimental infections with RFHV or RV2 rhadinovirus.